The prime objective of this research is to follow the psychosocial adaptation of a representative sample of the UCLA undergraduate student body and of a heterogeneous group of chronic marijuana users in an effort to determine the effects of long-term use of marijuana. The extent to which chronic marijuana use results in loss of motivation and impaired adjustment, and the extent to which the abuse of marijuana might be in itself a manifestation of pre-existing psychopathology will be investigated. The relationship between any change in trends of marijuana use and in individual characteristics and value systems will also be studied. Basic data will be provided by a questionnaire that has been completed by a 10 percent representative of the entire 1970-71 undergraduate UCLA student body and will be administered to a representative sample of each freshman class for the next four years. Follow-up data on the entire sample will be obtained by another questionnaire each year for four years. Follow-up will also be done on a heterogeneous sample of chronic users. Supplementary data on randomly selected individuals from the UCLA sample and the heterogeneous group of chronic users will be obtained from psychiatric interviews and psychological testing.